Abstract
Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is a mealybug of Southern African origin that has recently been introduced into Eastern Spain. It causes severe distortions on young citrus fruits and represents a growing threat to Mediterranean citrus production. So far, biological control has proven unsatisfactory due to the absence of efficient natural enemies in Spain. Hence, the management of this pest currently relies only on chemical control. The introduction of natural enemies of D. aberiae from the native area of the pest represents a sustainable and economically viable alternative to reduce the risks linked to pesticide applications. Since biological control of mealybugs has been traditionally challenged by taxonomic misidentification, an intensive survey of Delottococcus spp. and their associated parasitoids in South Africa was required as a first step towards a classical biological control programme. Combining morphological and molecular characterization (integrative taxonomy) a total of nine mealybug species were identified in this study, including three species of Delottococcus. Different populations of D. aberiae were found on wild olive trees, in citrus orchards and on plants of Chrysanthemoides monilifera, showing intra-specific divergences according to their host plants. Interestingly, the invasive mealybug populations from Spanish orchards clustered together with the population on citrus from Limpopo Province (South Africa), sharing COI haplotypes. This result pointed to an optimum location to collect natural enemies against the invasive mealybug. A total of 14 parasitoid species were recovered from Delottococcus spp. and identified to genus and species level, by integrating morphological and molecular data. A parasitoid belonging to the genus Anagyrus, collected from D. aberiae in citrus orchards in Limpopo, is proposed here as a good biological control agent to be introduced into Spain.
Highlights
Many mealybug species (Hemiptera: Pseudococcidae) are major pests that cause significant losses in crops and ornamental plants [1]
Five mealybug species were collected from citrus orchards: D. aberiae, Planococcus citri (Risso), Pseudococcus longispinus (Targioni Tozzetti), Paracoccus burnerae (Brain) and Ferrisia virgata (Cockerell)
A total of nine mealybug species were identified in this survey, three of them belonging to the genus Delottococcus (i.e. D. aberiae, D. phylicus and D. confusus)
Summary
Many mealybug species (Hemiptera: Pseudococcidae) are major pests that cause significant losses in crops and ornamental plants [1]. Encyrtid parasitoids have allowed for the effective control of important mealybug outbreaks, such as Maconellicoccus hirsutus (Green) [7] and Paracoccus marginatus Williams & Granara de Willink in the Caribbean [8,9] and Rastrococcus invadens Williams in West Africa [10,11] Besides these successes, there are well-documented examples of biological control programmes against mealybugs that have failed [4,5,12]. The misidentification of Phenacoccus manihoti MatileFerrero led to the ineffective introduction of Phenacoccus herreni Cox & Williams parasitoids into West Africa [13] Both cases were later amended through the correct identification of the target mealybugs and the introduction of host-specific parasitoids [5,14]. Some biological and behavioural characteristics relevant for biological control such as host preference may differ in closely-related natural enemies [16]
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